The present invention relates to a crimping tool for crimping lead end sleeves, contact sockets or lugs onto electrical conductors. More particularly it relates to a crimping tool which has crimping jaws which are arranged in the tool head section, are enclosed by a pivot lever and can be moved centrally relative to one another by the pivoting drive movement of the pivot lever effected by a toggle joint mechanism and thereby brought into and, on the return stroke, out of the crimping position. Its jaw surfaces partially abut in their active region form, together with the adjacent crimping jaws, a crimping aperture of adjustable cross section. An elastic compensation, automatically actuated during the crimping process and effected by springs, is created between parts of the force transmission system in order to compensate for differently dimensioned die profiles and the resulting variable crimping stroke.
The compensation of the respective crimping stroke produced by the differently dimensioned die profiles within the drive mechanics of the crimping tool existing between the handles and the crimping jaws is already necessary in order to guarantee the uniformity and quality of the crimping within a given size range of lead end sleeves and electrical conductors and in order to prevent breakage of tool parts by possible overloading. In this respect, it is particularly advantageous to provide this compensation in a resilient and elastic manner, e.g. by a spring element, which has been found in practice to considerably improve and facilitate the use of the crimping tools.
The crimping tool is ensured against possible premature opening of the crimping jaws by a pawl lock known in design and application. Once introduced, an operating stroke for the respective crimping is carried out in full in all cases.
In crimping tools with crimping jaws opening in a scissor-like manner, the compensation of crimping stroke differences has been effected in that only one of the mouth jaws is rigidly articulated. The other mouth jaw is articulated via an elastic zone, also in the form of a separate elastic element, to the associated handle with the interposition of the actuating member; e.g. a toggle lever mechanism (DE-PS 3109 289).
In contrast, in crimping tools designed according to the generic type, the compensation of the crimping stroke difference can be designed in such a manner that an elastically acting support, which is expediently formed by a separate elastic element, is arranged on at least one of the force transmitting elements (EP-PS O158 611). In this case, a toggle lever belonging to the force transmitting system is constructed at its outer hinged point so as to be displaceable against the action of a tension spring and is thereby able to adapt to a limited degree, together with a pawl lock, to the profile which is to be crimped. This type of indirect elastic support of the pivot lever accommodating the crimping jaws must be regarded as disadvantageous in many respects, since crimping errors which can occur in the degree of completion of the crimping can go unnoticed and therefore cannot be ruled out.
Crimping tools according to the generic features for crimping lead end sleeves onto electrical conductors have crimping jaws which are arranged in the tool head section, are enclosed by a pivot lever formed by the tool limb and can be displaced centrally relative to one another by the pivoting movement of the pivot lever. Thereby they can be brought into and out of the crimping position (U.S. Pat. No. 3,203,078).
In this type of crimping tool, the pivot lever is brought into a drive connection with the crimping jaws via a splined shaft profile, and the pivot lever is accommodated and displaceable in a centring fashion on the outer peripheral surfaces of the crimping jaws. The crimping jaws are pivotably mounted and axially fixed to the lower base plate of one crimping tool part on through bearing pins.
Because of the type and shape of the die and also the design of the structural operating elements, the crimping tool proposed here is unsuitable for crimping lead end sleeves. The latter require crimping which is complete on all sides, is as uniform as possible over the entire cross section and has precise dimensions, which cannot be achieved using crimping tools of this type.
Further known tool designs for crimping electrical conductors are illustrated and described in U.S. Pat. No. 5,261,263, U.S. Pat. No. 3,199,335, GB-PS 886,259 and GB-PS 1,324,253. These tool designs are also unsuitable for meeting the current demands of connecting or crimping technology in power electronics in terms of providing crimping which has shape precision, is non-destructive and secure. Furthermore, they are neither suitable for repeated crimping, nor are they simple and easy to handle. Whilst the structural operating features have been complicated in design and require relatively high technological outlay, it is also precisely these elements which impair the operating properties of these crimping tools as regards high operating position precision and a low degree of operational disturbance.
It is also true that multi-surface crimping tools of this type require very precise movement of the crimping jaws, particularly in the case of small and miniature crimping dimensions, for instance in the range below 1 mm.sup.2, and therefore require a similarly precise drive or force transmission system and springing system between the displaced crimping tool parts.
To date, known designs of this type of crimping tool cannot fulfil the expectations in practice, or can only fulfil them to an unsatisfactory degree. It is these circumstances which have given rise to the purpose and object of the present invention.